1 Scope
NOTE This standard covers the design documentation requirements, materials, installation, testing, and acceptance criteria for pre-action and deluge fire sprinkler systems. (1.1)
NOTE These systems share a defining characteristic that distinguishes them from both wet-pipe and conventional dry-pipe systems: the distribution piping is normally dry, and water is admitted to the piping by a pre-action valve or deluge valve that is operated by a separate, independent fire detection system rather than by the opening of a sprinkler alone. (1.2)
NOTE The detection system, arranged and listed for releasing service, is the primary actuating event, and the releasing control unit, not the sprinkler, decides when water enters the pipe. (1.3)
1.4The scope extends from the supply-side connection at the pre-action or deluge valve assembly — including the valve trim, the priming and pilot lines, the supervisory air or nitrogen supply, the solenoid and pneumatic actuators, the manual release, the intermediate chamber drain, and the main drain — through all above-ground supply mains, cross mains, branch lines, and end connections to the individual sprinklers or open nozzles.
1.5The releasing detection and control system, low-point auxiliary drains, valve supervisory devices, the waterflow alarm, the fire department connection, system pitch and drainage, hangers and seismic bracing, and the air or nitrogen supply are included.
NOTE The hydraulic design, the system volume, and the detection-to-discharge response time govern all of these components together as an integrated suppression and detection system. (1.6)
1.7Pre-action and deluge systems installed under this standard shall comply with NFPA 13, NFPA 72 (for the detection and releasing functions), the International Fire Code (IFC), and the International Building Code (IBC) as adopted locally.
1.8Where local amendments modify NFPA 13 or NFPA 72 requirements, the local amendment shall govern unless it is less stringent than the base standard, in which case the base standard governs.
1.9The Contractor and the designer shall confirm the editions of NFPA 13 and NFPA 72 adopted in the jurisdiction prior to beginning design work.
NOTE Successive editions have changed system volume limits, water delivery time rules, design-area penalties for double-interlock systems, releasing circuit requirements, and corrosion protection that affect both design and material procurement. (1.10)
1.11This standard does not govern foam-water deluge or foam-deluge systems that require foam concentrate, proportioning equipment, and the additional design rules of NFPA 11 and NFPA 16.
1.12This standard does not govern occupancy-specific or commodity-specific systems designed under the storage chapters of NFPA 13, which require specialized density, area, in-rack sprinkler, and water-delivery analysis beyond the scope of this document.
1.13The Engineer of Record shall confirm whether foam or storage-specific rules apply to any portion of the project before releasing this standard for use.
2 Differentiation from Wet-Pipe and Dry-Pipe Systems
2.1Pre-action and deluge systems are the most mechanically and electrically complex water-based suppression systems; they introduce a separate detection system, a releasing control unit, electrical releasing circuits, and a valve actuation chain, each of which is an additional component that shall be designed, installed, supervised, tested, and maintained.
Single-interlock pre-action (water-sensitive, high-value, closed heads)
Double-interlock pre-action (freezer / refrigerated, closed heads)
Deluge (high-hazard, open heads, total-area discharge)
Multiple systems on this project — see drawings
Data center or computer equipment room
Telecommunications or electrical equipment room
Archive, library, museum, or records storage
Freezer or refrigerated warehouse (double-interlock)
Clean room or laboratory
Transformer or oil-filled equipment room (deluge)
Aircraft hangar (deluge — see also NFPA 409)
Flammable / combustible liquid or chemical process (deluge)
Combustible conveyor (deluge)
Other — see basis of design
2.2A pre-action or deluge system shall not be substituted for a wet-pipe or dry-pipe system where the simpler system is appropriate.
2.3The justification for the added complexity of a pre-action or deluge system shall be documented by the Engineer of Record in the basis-of-design narrative.
NOTE A single-interlock or double-interlock pre-action system is selected when the protected space is water-sensitive or high-value and an accidental discharge from a physically damaged sprinkler or fitting would cause unacceptable loss. (2.4)
NOTE The pre-action interlock keeps water out of the piping until a fire is independently confirmed by detection, so a broken sprinkler in an empty room leaks air, not water. (2.5)
NOTE A double-interlock pre-action system is the standard choice for freezer and refrigerated warehouses, where a single-interlock system would still admit water on detection alone and where the operators want both a detection event and a sprinkler event to coincide before water enters the pipe. (2.6)
2.7A deluge system is selected when the hazard is severe enough that water shall be applied simultaneously over an entire area the instant a fire is detected, faster than sequential sprinkler operation can achieve.
NOTE Deluge systems use open sprinklers or spray nozzles with no thermal element, so every device on the system discharges together when the deluge valve trips. (2.8)
NOTE Representative deluge applications are transformer and oil-filled equipment rooms, aircraft hangars, flammable and combustible liquid handling and process areas, chemical plants, and combustible conveyors where a fire can spread along the line faster than individual heads would open. (2.9)
3 Referenced Standards
3.1Materials, design, installation, and testing shall comply with the current adopted editions of the following standards.
| Standard |
Title |
| NFPA 13 |
Standard for the Installation of Sprinkler Systems |
| NFPA 20 |
Standard for the Installation of Stationary Pumps for Fire Protection |
| NFPA 24 |
Standard for the Installation of Private Fire Service Mains and Their Appurtenances |
| NFPA 25 |
Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems |
| NFPA 70 |
National Electrical Code |
| NFPA 72 |
National Fire Alarm and Signaling Code |
| NFPA 291 |
Recommended Practice for Fire Flow Testing and Marking of Hydrants |
| NFPA 409 |
Standard on Aircraft Hangars |
| IBC |
International Building Code |
| IFC |
International Fire Code |
| ASTM A53 |
Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless |
| ASTM A135 |
Standard Specification for Electric-Resistance-Welded Steel Pipe |
| ASTM A234 |
Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service |
| ASTM A795 |
Standard Specification for Black and Hot-Dipped Zinc-Coated (Galvanized) Welded and Seamless Steel Pipe for Fire Protection Use |
| ASME B16.5 |
Pipe Flanges and Flanged Fittings |
| ASME B16.9 |
Factory-Made Wrought Buttwelding Fittings |
| ASME B16.11 |
Forged Fittings, Socket-Welding and Threaded |
| UL 199 |
Automatic Sprinklers for Fire Protection Service |
| UL 260 |
Dry Pipe Valves for Fire Protection Service |
| UL 262 |
Gate Valves for Fire Protection Service |
| UL 312 |
Check Valves for Fire Protection Service |
| UL 753 |
Alarm Accessories for Automatic Water-Supply Control Valves for Fire Protection Service |
| UL 864 |
Control Units and Accessories for Fire Alarm Systems |
| UL 1091 |
Butterfly Valves for Fire Protection Service |
| UL 2017 |
General-Purpose Signaling Devices and Systems |
| FM Global 1011-1014 |
Approval Standard for Deluge and Pre-Action Valves and Their Trim |
| FM Global 2024 |
Approval Standard for Air Maintenance Devices for Sprinkler Systems |
| FM Global DS 2-0 |
Installation Guidelines for Automatic Sprinklers |
| FM Global DS 2-8N |
Corrosion in Automatic Sprinkler Systems |
| ANSI/AWWA C606 |
Grooved and Shouldered Joints |
3.2Where standards conflict, the more stringent requirement shall govern unless directed otherwise by the Engineer of Record in writing.
4 Submittals
4.1 Action Submittals
4.1.1The Contractor shall submit the following for the Engineer of Record's review and the Authority Having Jurisdiction's approval prior to procurement and installation.
4.1.2The submittal package shall demonstrate compliance on two fronts at once: the hydraulic and water-delivery performance of the water side under NFPA 13, and the detection, releasing, and sequence-of-operation performance of the detection side under NFPA 72.
NOTE The two sides are coordinated through a single document — the sequence of operations (releasing matrix) — that the AHJ uses to confirm that the right detection event causes the right valve to release at the right time. (4.1.3)
4.1.4The following items shall be submitted as a coordinated package:
- Working drawings for the sprinkler system complying with NFPA 13 Chapter 28, including floor plans showing pipe routing, pipe sizes, sprinkler or open-nozzle types and locations, elevations, riser diagrams, the hydraulic reference node diagram, and pitch and drainage details with all auxiliary drain locations
- A releasing matrix (sequence of operations) identifying each initiating device or zone, the cross-zoned logic, the releasing output to each pre-action or deluge valve, the alarm and supervisory outputs, and any interlocks to HVAC, dampers, door release, or equipment shutdown
- Detection and releasing system drawings complying with NFPA 72, including detector layout and spacing, the releasing control unit, releasing circuit class and survivability, manual release station locations, end-of-line supervision, and battery / secondary power calculations
- Hydraulic calculations performed by the pipe-sizing method, demonstrating that the system meets the design density and area for each hazard area, with the demand plotted against the supply curve including hose stream allowances and the required safety margin demonstrated at the design point
- A calculated system volume and, where required by NFPA 13, a water delivery time calculation demonstrating that water reaches the inspector's test connection within the applicable time limit (double-interlock pre-action and deluge systems are treated as dry-pipe systems for water delivery purposes)
- Trip-time calculations for the pre-action or deluge valve demonstrating that the valve operates and water is delivered within the time assumed in the sequence of operations
- Product data and listings for the pre-action or deluge valve and trim, the releasing solenoid, the releasing control unit, all detectors, the air maintenance device or nitrogen generator (pre-action), all sprinklers or open nozzles, valve supervisory switches, the waterflow alarm device, the fire department connection, and hangers
- Manufacturer's installation instructions for the valve, the releasing control unit, and the detection devices, including any limitations on application, system arrangement, supervisory air tolerance, or releasing circuit compatibility
- A pipe pitch and drainage plan showing all low points, auxiliary drains, the main drain, and elevation callouts confirming compliance with the minimum pitch required by NFPA 13
- Seismic bracing calculations, where required by the project's Seismic Design Category
☐ Working drawings per NFPA 13 Chapter 28
☐ Releasing matrix / sequence of operations
☐ Detection and releasing drawings per NFPA 72
☐ Hydraulic calculations
☐ System volume and water delivery time calculation
☐ Valve trip-time calculations
☐ Product data and listings for valve, releasing panel, detectors
☐ Manufacturer installation instructions
☐ Pipe pitch and drainage plan with auxiliary drain locations
☐ Battery / secondary power calculations
☐ Seismic bracing calculations (if required)
4.1.5No work shall proceed on any portion of the pre-action or deluge system until the corresponding submittals are reviewed, returned, and any required approval from the AHJ is in hand.
4.1.6Working drawings shall be prepared by or under the supervision of a person with qualifications acceptable to the AHJ.
4.1.7The Contractor shall confirm designer qualification requirements for both the water-side and detection-side disciplines before assigning the design work.
NOTE The water-side layout shall be prepared by a licensed fire protection engineer or a NICET-certified sprinkler designer, and the detection and releasing design by a person holding NICET certification in fire alarm systems or a licensed engineer, as required by the jurisdiction. (4.1.8)
4.2 Closeout Submittals
4.2.1The following shall be submitted at substantial completion before the system is accepted:
- Contractor's Material and Test Certificate for Aboveground Piping (NFPA 13 Figure 29.1.1), signed by the installing contractor, certifying materials, joint types, flushing, hydrostatic test, air pressure test (pre-action), valve trip test, water delivery time, and alarm and supervisory device operation
- Record of Completion and inspection/test forms for the detection and releasing system per NFPA 72, signed by the fire alarm contractor
- As-built drawings reflecting field changes from the reviewed working drawings, including the as-built releasing matrix
- Operation and maintenance manual including valve impairment and reset procedures, releasing panel programming record, detector sensitivity records, air or nitrogen supply maintenance, seasonal drainage procedures, and NFPA 25 and NFPA 72 inspection intervals
- Warranty documentation for all components carrying a manufacturer warranty
- Hydraulic and water delivery design information signs confirming the installed signs match the design calculations
- Air leakage test record for pre-action systems demonstrating compliance with the NFPA 13 air-leakage limit
☐ Contractor's Material and Test Certificate for Aboveground Piping
☐ NFPA 72 Record of Completion for detection / releasing
☐ Valve trip test record with water delivery time
☐ Air leakage test record (pre-action)
☐ As-built drawings and as-built releasing matrix
☐ Operation and maintenance manual with panel programming record
☐ Manufacturer warranty documentation
☐ Hydraulic and water delivery design information signs
4.2.2The Contractor shall submit the closeout submittal items listed above at substantial completion before the system is accepted.
5 Quality Assurance
5.1 Installer Qualifications
5.1.1Because these systems combine a water-based system and a detection/releasing system, the installing entity shall hold, or shall engage subcontractors holding, both a fire protection (sprinkler) contractor's license and a fire alarm contractor's license as required locally.
5.1.2Pre-action and deluge system installation shall be performed by a licensed fire protection contractor as required by the state and local jurisdiction.
5.1.3The individual preparing the sprinkler working drawings and hydraulic calculations shall hold qualifications acceptable to the AHJ.
5.1.4Where state law requires NICET certification, the sprinkler designer shall hold NICET Level III or IV in water-based systems layout and the detection designer shall hold NICET certification in fire alarm systems, as applicable.
5.1.5Where the Contractor's in-house staff lacks experience in system volume sizing, water delivery time analysis, releasing circuit design, cross-zoned detection logic, and integration of the valve actuation chain with the releasing control unit, the design shall be subcontracted to or peer-reviewed by qualified specialists.
5.1.6The Contractor shall identify both the sprinkler design lead and the detection design lead on the working drawings.
5.2 Coordination with Other Trades
5.2.1The sprinkler Contractor shall coordinate early and continuously with the fire alarm, mechanical, electrical, structural, and architectural trades.
5.2.2The pre-action or deluge valve room or enclosure shall be in a heated space adjacent to the protected area.
5.2.3The releasing control unit shall be provided with conditioned space, dedicated power, and secondary (battery) power.
5.2.4The air compressor or nitrogen generator (pre-action) requires dedicated electrical service and possibly ventilation.
5.2.5Auxiliary drains shall be accessible at every low point.
5.2.6The releasing matrix shall be coordinated with HVAC shutdown, damper closure, and any equipment power-down required when the valve releases.
5.2.7The location and structural capacity of the structure to which hangers and seismic braces attach shall be confirmed with the structural engineer before hanger installation.
5.2.8Hanger design loads shall account for the water-filled pipe weight plus an allowance for residual water remaining after a release.
5.3 Listing and Approval
5.3.1All sprinklers and open nozzles, pre-action and deluge valves, releasing solenoids, releasing control units, detection devices, air maintenance devices, nitrogen generators, valves, hangers, seismic brace assemblies, and alarm devices shall be listed by a Nationally Recognized Testing Laboratory (UL, FM, or another NRTL accepted by the AHJ) for the specific application and service conditions.
5.3.2Sprinklers shall be listed to UL 199 and open nozzles to their applicable listing.
5.3.3The releasing control unit shall be listed to UL 864 for releasing service; a general-purpose fire alarm control unit that is not specifically listed for releasing service shall not be used to operate a pre-action or deluge valve.
5.3.4The releasing solenoid and the valve shall be listed together as a compatible combination, and mixing solenoid and valve from different manufacturers is not permitted unless the combination is independently listed.
5.4 FM Global Compliance
5.4.1Where the building's property insurance carrier or the Owner requires FM Global compliance, all components shall be FM-approved in addition to UL-listed.
○ Not required
○ Required — FM-approved components throughout
5.4.2Where the building's property insurance carrier or the Owner requires FM Global compliance, all components shall be FM-approved in addition to UL-listed.
NOTE FM and UL listings are not identical, and cross-zoned detection arrangements accepted under one listing or jurisdiction may not be accepted under another. (5.4.3)
5.4.4The Contractor shall confirm approval status for each product and each detection arrangement at procurement, not after installation.
5.5 Corrosion Protection
NOTE Internal corrosion is an aggressive problem in pre-action and deluge systems: residual water trapped at low points after testing or a release, combined with the oxygen in the supervisory air (pre-action) or the open atmosphere (deluge), drives microbiologically influenced corrosion (MIC) and oxygen pitting that can perforate the pipe wall over the service life. (5.5.1)
○ Galvanized steel pipe throughout, air supervised (pre-action)
○ Black steel pipe, nitrogen inerted (pre-action)
○ Galvanized steel pipe, nitrogen inerted (pre-action, enhanced)
○ Galvanized steel pipe, complete drainage (deluge)
5.5.2For pre-action systems the Contractor shall provide one of three corrosion-mitigation approaches: galvanized steel pipe throughout; nitrogen inerting using a listed nitrogen generator that displaces oxygen; or both, where the Owner's risk profile or insurance requirements warrant enhanced protection.
NOTE NFPA 13 recognizes nitrogen inerting as an alternative to galvanized pipe for corrosion control on supervised dry systems, and nitrogen is the default for long-life critical assets such as data centers and freezer warehouses. (5.5.3)
5.5.4Deluge piping, being open to atmosphere, shall not be nitrogen-inerted; deluge piping shall be galvanized and shall be designed to drain completely after each release and test.
6 Environmental and Service Conditions
6.1 Temperature Range
6.1.1The valve trim, priming water, pilot lines, and supply-side piping shall not be allowed to freeze.
-40100
-40-20324070100
Default: 70 °F
4070
40506070
Default: 50 °F
6.1.2The valve and its trim shall be installed in a heated enclosure or valve room maintained at not less than 40°F (4°C) at all times.
6.1.3Where the protected space is a freezer or refrigerated room, the designer shall account for the temperature differential at the valve-room-to-cold-space boundary and shall provide insulation, heat trace, or vapor barriers as required to prevent moisture migration into the dry piping during defrost cycles.
6.1.4A single-interlock system shall not be used in a freezer, because it admits water on detection alone, before any sprinkler opens, filling cold piping with water that will freeze.
NOTE The double interlock exists specifically so that water is not admitted to freezer piping until a sprinkler has also opened. (6.1.5)
6.2 Maximum Working Pressure
6.2.1On a pre-action system the supervisory air pressure shall be maintained within the range specified by the valve manufacturer's listing; differential pre-action valves require the air pressure to be held above a manufacturer-specified value to keep the clapper seated, while low-differential and electrically operated valves hold by other means and use a lower supervisory pressure.
40250
100125150175200250
Default: 150 psi
760
7101520254060
Default: 20 psi
6.2.2The system working pressure shall not exceed 175 psi at the valve unless the system and components are rated for a higher pressure.
6.2.3Where the water supply static pressure exceeds 175 psi, a listed pressure-reducing valve shall be provided.
7 Design Basis and Hazard Classification
7.1 Occupancy Hazard Classification
NOTE Hazard classification determines the design density, the design area, and therefore the flow and pressure demand on the water supply. (7.1.1)
Light Hazard
Ordinary Hazard Group 1
Ordinary Hazard Group 2
Extra Hazard Group 1
Extra Hazard Group 2
Special hazard — deluge, engineered density
Multiple hazard areas — see drawings
7.1.2The hazard classification shall be assigned by the designer based on the occupancy descriptions in NFPA 13 Chapter 5 and confirmed with the Owner and the AHJ before the hydraulic design is finalized.
NOTE Pre-action systems most commonly protect Light Hazard and Ordinary Hazard occupancies, while archives and records storage may be Light Hazard or may invoke the storage rules. (7.1.3)
NOTE Deluge systems are typically applied to Extra Hazard and special-hazard occupancies where the density is high and the design covers the entire deluge zone, not a calculated remote area. (7.1.4)
7.2 Design Density and Area
7.2.1Design density and area shall be determined from NFPA 13 for the applicable hazard classification, with the system-type adjustment applied.
7.2.2The adjustment is the single most important design-basis distinction among the three system types covered by this standard, and the designer shall apply it correctly.
○ Single-interlock pre-action — wet-pipe design area (no 30% increase)
○ Double-interlock pre-action — wet-pipe area increased 30% (dry-pipe rule)
○ Deluge — entire zone area, all heads flowing simultaneously
0.10.6
0.10.150.20.30.40.450.6
Default: 0.15 gpm/ft²
15006500
1500195026003250390052006500
Default: 1950 ft²
7.2.3A single-interlock pre-action system admits water on detection alone, typically before the sprinklers open, so NFPA 13 does not apply the 30 percent design-area increase to it; it is treated, for area purposes, like a wet-pipe system at the same hazard classification.
7.2.4NFPA 13 requires the design area for a double-interlock pre-action system to be increased by 30 percent over the wet-pipe area for the same hazard, without revising the density, exactly as for a dry-pipe system.
7.2.5The 30 percent increase for a double-interlock pre-action system is mandatory and shall not be reduced by engineering judgment.
7.2.6A deluge system discharges from every open device the instant the valve trips, so the design covers the entire area served by the deluge zone at the required density, with no remote area because all heads flow at once.
7.2.7The water supply and fire pump shall be sized for simultaneous flow from every open device in the deluge zone, or in multiple zones where the design assumes more than one zone may operate together.
7.3 Hose Stream Allowance
NOTE The hose stream allowance is the same as for a wet-pipe system at the same hazard classification: 100 gpm for light hazard, 250 gpm for ordinary hazard, and 500 gpm for extra hazard. (7.3.1)
100 gpm (Light Hazard)
250 gpm (Ordinary Hazard)
500 gpm (Extra Hazard)
7.3.2The hose stream demand shall be applied simultaneously with the sprinkler or deluge demand.
7.4 Water Supply Verification
NOTE Because deluge demand is large with all heads flowing, deluge systems frequently require a fire pump. (7.4.1)
Public water main — flow test required
Dedicated fire water storage tank and pump
Combined public main and storage tank
20150
405060708090100120150
Default: 70 psi
10130
20304050607080100130
Default: 50 psi
7.4.2Water supply data shall be obtained by a hydrant flow test conducted at or near the project site in accordance with NFPA 291, no more than 12 months prior to the date of submittal.
7.4.3Static pressure, residual pressure, and pitot flow shall be recorded.
7.4.4The designer shall plot the supply curve and confirm that the system demand including hose stream falls below the supply curve with the safety margin required by NFPA 13.
7.4.5Where the available supply does not meet the demand, a fire pump shall be provided per Fire Pumps. 8 System Types
8.1 Single-Interlock Pre-Action
NOTE A single-interlock pre-action system uses closed (automatic) sprinklers on piping that is held under supervisory air or nitrogen, and it admits water to the piping on the operation of the detection system alone. (8.1.1)
NOTE When a detector operates, the releasing control unit energizes the release solenoid (or trips a pneumatic actuator), the pre-action valve opens, and water fills the piping up to the still-closed sprinklers; water then discharges only when a sprinkler subsequently opens from heat. (8.1.2)
1001000
2505007501000
Default: 1000 heads
8.1.3The single interlock provides one layer of protection against accidental discharge: a physically broken sprinkler or fitting in a room with no fire releases supervisory air and signals a trouble condition, but it does not admit water, because no detector has operated.
8.1.4Single-interlock systems are limited by NFPA 13 to no more than 1,000 automatic sprinklers controlled by any single pre-action valve.
8.1.5Because water arrives on detection before the sprinklers open, the single-interlock system does not take the 30 percent design-area penalty.
8.2 Double-Interlock Pre-Action
NOTE A double-interlock pre-action system also uses closed sprinklers on supervised dry piping, but it requires two coincident events before water is admitted: a detection event and a loss of supervisory air pressure caused by a sprinkler opening or by piping damage. (8.2.1)
NOTE Only when the releasing control unit sees both signals — typically a cross-zoned detection signal and a low-air signal — does it energize the release solenoid to open the valve. (8.2.2)
NOTE The double requirement makes the system suitable for freezers, because water is not admitted to the cold piping on a detector alone, so a false detector signal in an empty freezer does not fill the piping. (8.2.3)
8.2.4A double-interlock system is treated as a dry-pipe system for water delivery time and for the 30 percent design-area increase.
8.3 Deluge
NOTE A deluge system uses open sprinklers or spray nozzles — there is no thermal element — on piping that is open to atmosphere downstream of the deluge valve. (8.3.1)
NOTE The deluge valve is held closed only by the pilot/priming arrangement, not by system pressure on the discharge side, and it is operated by the detection system through the releasing control unit. (8.3.2)
NOTE When the valve trips, water flows to every open device simultaneously and discharges over the entire protected zone at once. (8.3.3)
8.3.4Deluge systems shall be used where the hazard demands immediate total-area application, such as transformer and oil-filled equipment, aircraft hangars, flammable liquid and chemical process areas, and combustible conveyors.
8.3.5Because the piping is open, a deluge system is not air-supervised; instead the detection circuit, the valve actuation, and the open-nozzle layout shall be supervised and tested, and the piping shall be designed to drain completely after each operation.
9 Releasing Detection and Control
9.1 Releasing Control Unit
NOTE The releasing control unit monitors the initiating devices, executes the releasing logic defined in the sequence of operations, energizes or de-energizes the release solenoid depending on the listed arrangement, and transmits alarm, supervisory, and trouble signals to the building fire alarm system or supervising station. (9.1.1)
9.1.2The detection and releasing function shall be provided by a control unit listed to UL 864 for releasing service and installed in accordance with NFPA 72.
9.1.3A general-purpose fire alarm control unit not specifically listed for releasing service shall not operate a pre-action or deluge valve.
9.1.4The releasing control unit shall be provided with secondary (battery) power sized to carry the system through the standby and alarm periods required by NFPA 72.
9.1.5The releasing circuits shall meet the class and survivability required by NFPA 72 for the application.
9.2 Detection Type and Layout
NOTE The choice of detection device depends on the speed of detection required, the environment (temperature, dust, airflow, ceiling height), and the hazard. (9.2.1)
Spot smoke detectors
Spot heat detectors (fixed-temperature / rate-of-rise)
Linear (line-type) heat detection cable
Optical flame detectors (UV / IR)
Pneumatic rate-of-rise detection
Combination — see releasing matrix
9.2.2Detection devices shall be selected and spaced for the hazard and the protected environment in accordance with NFPA 72.
9.2.3Detection devices shall be of a type listed for releasing service.
NOTE Flame detectors are common over flammable liquid and transformer hazards where the fastest possible response is required; linear heat detection suits cable trays and conveyors; spot smoke detection suits data centers and clean rooms where incipient detection is valued. (9.2.4)
9.3 Cross-Zoned Detection
NOTE Cross-zoning guards against an accidental release from a single faulty or transient detector signal, which is exactly the failure mode that pre-action and deluge systems exist to prevent. (9.3.1)
○ Cross-zoned detection (two zones / two detectors required)
○ Single detection zone (where accepted by AHJ)
○ Double interlock — cross-zoned detection AND low-air signal
9.3.2For releasing service, where cross-zoned (coincidence) logic is used, two separate detection zones or two separate detectors shall operate before a release signal is issued.
9.3.3On a single-interlock pre-action system, cross-zoned detection alone releases the valve.
9.3.4On a double-interlock pre-action system, the releasing logic requires a cross-zoned (or single-zone, per the listing) detection signal together with the low-air signal.
9.3.5The Contractor shall confirm acceptance of the proposed cross-zoning arrangement with the AHJ and, where applicable, the insurer before finalizing the design, because cross-zoned detection is not accepted in every jurisdiction and is not universally FM-approved.
9.4 Manual Release and Abort
9.4.1Where the sequence of operations and the AHJ permit, an abort or delay function may be provided.
☐ Manual release station (releasing-service listed)
☐ Manual emergency release at valve
☐ Abort / delay function (only where AHJ permits)
9.4.2A manual release station shall be provided at the protected area or at the valve, listed for releasing service, allowing trained personnel to trip the valve manually.
9.4.3Abort and delay functions shall be applied only where they are explicitly permitted, because they introduce a delay into a life-safety releasing function.
9.4.4The manual release shall remain capable of operating the valve independent of the abort function.
10 Valves and Trim
10.1 Pre-Action / Deluge Valve
NOTE The pre-action or deluge valve is a listed valve held closed by a pilot/priming arrangement and operated by the releasing solenoid (electric release), a pneumatic actuator (pneumatic release), or both, in the combination defined by the system type and the listing. (10.1.1)
NOTE On electric release, the releasing control unit energizes or de-energizes the solenoid to vent the priming chamber and allow the valve to open. (10.1.2)
○ Single-interlock pre-action valve (electric release)
○ Double-interlock pre-action valve (electric/pneumatic release)
○ Deluge valve (electric release)
○ Deluge valve (electric/pneumatic release)
○ Electric release (solenoid from releasing control unit)
○ Pneumatic release (pilot line / dry pilot actuator)
○ Electric and pneumatic (double interlock)
2 in.
2-1/2 in.
3 in.
4 in.
6 in.
8 in.
10.1.3The valve and the releasing solenoid shall be listed together as a compatible assembly.
NOTE Diaphragm valves are common on modern pre-action and deluge systems because a single valve body can be trimmed for single-interlock, double-interlock, or deluge service by changing the trim and release arrangement. (10.1.4)
10.2 Valve Trim
10.2.1The valve assembly shall be furnished with the manufacturer's standard listed trim for the selected system type.
10.2.2The valve assembly shall be furnished with the manufacturer's standard listed trim for the selected system type, and the trim shall not be field-assembled from non-listed parts.
10.2.3The trim shall include a water-side pressure gauge and, on pre-action systems, a supervisory air/nitrogen-side gauge.
10.2.4The trim shall include the priming line and pressure-operated relief or alarm port, and the release solenoid with its supervised wiring.
10.2.5On pre-action systems the trim shall include a low-air supervisory switch, and on double-interlock systems that low-air switch shall be wired into the releasing interlock.
10.2.6The trim shall include an intermediate chamber drain with sight observation to confirm the chamber is dry before resetting.
10.2.7The trim shall include a main drain valve not smaller than 2 in., an automatic ball drip on the FDC supply piping, and the waterflow alarm pressure switch that signals when water enters the piping.
10.3 Supervisory Air / Nitrogen Supply
10.3.1Pre-action systems shall be maintained under supervisory air or nitrogen so that the loss of pressure from an opened sprinkler or damaged pipe is detected.
NOTE Deluge systems are open to atmosphere and are not air-supervised. (10.3.2)
○ Dedicated air compressor with listed air maintenance device
○ Plant air through listed air maintenance device
○ Membrane nitrogen generator
○ Pressure-swing adsorption (PSA) nitrogen generator
○ Not applicable — deluge (open to atmosphere)
1560
15304560
Default: 30 min
10.3.3Where the supervisory gas is air, an air compressor with a listed air maintenance device shall be provided, and the air maintenance device shall limit the rate of air introduction so that a small leak is not masked by an oversized restoration capacity.
10.3.4Where the supervisory gas is nitrogen, a listed nitrogen generator (membrane or pressure-swing adsorption) shall be provided, producing at least 98 percent nitrogen at the valve and purged to the listed purity at the most remote sprinkler.
NOTE Nitrogen is the preferred supervisory gas for data centers and freezer warehouses because it eliminates the oxygen that drives internal corrosion over the long service life of these critical assets. (10.3.5)
10.4 Valve and Detection Supervision
☐ Main control valve tamper switch
☐ Low air / nitrogen pressure switch (pre-action)
☐ Release solenoid circuit supervision
☐ Detection circuit supervision
☐ Valve room low-temperature switch (40°F)
10.4.1The water supply control valve and any other valves controlling water to the system shall be supervised open by an electrically supervised tamper switch connected to the fire alarm system or supervising station per NFPA 72 and NFPA 13.
10.4.2The release solenoid wiring, the detection circuits, and, on pre-action systems, the supervisory air pressure shall all be electrically supervised so that any open, ground, loss of solenoid continuity, or low-air condition produces a trouble signal.
10.4.3NFPA 13 requires the system piping and the detection devices to be automatically supervised where there are more than 20 sprinklers on the system.
11 Piping and Sprinklers
11.1 Closed Heads (Pre-Action) vs. Open Heads (Deluge)
NOTE Pre-action systems use closed (automatic) sprinklers in which the thermal element holds the orifice closed until heat opens the individual sprinkler; deluge systems use open sprinklers or directional spray nozzles with no thermal element, every device permanently open and discharging the instant the valve trips. (11.1.1)
Closed upright sprinklers (pre-action)
Closed dry-pendent / dry-sidewall sprinklers (pre-action)
Open sprinklers (deluge)
Open directional spray nozzles (deluge)
Multiple types — see drawings
K-5.6 (standard commercial)
K-8.0 (large orifice)
K-11.2 (extra large orifice)
K-14.0
Multiple K-factors — see drawings
○ Standard Response
○ Quick Response
○ Not applicable — open heads (deluge)
Ordinary (135°F–170°F)
Intermediate (175°F–225°F)
High (250°F–300°F)
Not applicable — open heads (deluge)
11.1.2Pre-action systems shall use closed (automatic) sprinklers listed to UL 199.
11.1.3Standard pendent sprinklers shall not be used where residual water could collect and freeze; upright and listed dry-pendent sprinklers are the common orientations in pre-action service.
11.1.4Open nozzles for deluge service shall be selected for the discharge pattern, K-factor, and throw required by the hazard, and shall be installed in the orientation and at the spacing on which the hydraulic design is based.
11.2 Piping Materials and Corrosion Control
11.2.1Steel pipe shall conform to ASTM A795 or ASTM A53; ASTM A795 is the purpose-written fire protection standard and is preferred.
NOTE The galvanized variant is strongly preferred over black for these normally dry systems unless a pre-action system is also nitrogen-inerted, because internal corrosion in cycled wet-dry environments is significantly more aggressive than in continuously wet systems. (11.2.2)
○ ASTM A795 (galvanized) — preferred
○ ASTM A795 (black) — pre-action with nitrogen inerting only
○ ASTM A53 (galvanized)
○ ASTM A53 (black) — pre-action with nitrogen inerting only
Threaded (Schedule 40 only, 3 in. and smaller)
Grooved mechanical coupling (listed, 1 in. and larger)
Welded (Schedule 40, 1 in. and larger)
Grooved mains / threaded branch lines
11.2.3Steel pipe shall conform to ASTM A795 or ASTM A53, with ASTM A795 preferred.
11.2.4Schedule 40 pipe shall be used for threaded joints in sizes 3 in. and smaller; Schedule 10 listed for dry-system service or Schedule 40 may be used for grooved or welded joints.
11.2.5Schedule 10 pipe shall not be threaded.
11.2.6CPVC pipe shall not be used.
11.2.7Galvanized pipe that is field-cut, threaded, or welded shall be touched up with a listed cold-galvanizing compound to restore the corrosion protection at the most corrosion-prone location in the system.
11.2.8Galvanized fittings shall be used with galvanized pipe.
11.2.9Threaded joints shall use listed fire protection thread sealant applied to male threads only, and PTFE tape shall not be the sole sealant.
11.2.10On pre-action systems, threaded joints shall be assembled for air-tightness as well as water-tightness because the system shall meet the air-leakage limit.
11.2.11Grooved coupling gaskets shall be compatible with the supervisory gas (EPDM is acceptable for air and nitrogen) and the coupling torque shall be confirmed at every joint.
11.2.12Welding shall be performed by qualified welders, weld joints visually inspected for full penetration, and galvanized pipe weld areas repaired with cold-galvanizing compound.
12 Drainage
12.1 Pipe Pitch
NOTE Pitch is the primary mechanism by which residual water — from a hydrostatic test, a release, condensation, or a partial trip-and-reset — is removed. (12.1.1)
NOTE Inadequate pitch leaves trapped water that corrodes the pipe and, in cold applications, freezes and ruptures it. (12.1.2)
0.52
0.511.52
Default: 0.5 in per 10 ft
0.251
0.250.50.751
Default: 0.25 in per 10 ft
12.1.3System piping shall be pitched to drain back to the valve or to auxiliary drains at low points.
12.1.4NFPA 13 requires minimum pitch of 1/2 in. per 10 ft for branch lines and 1/4 in. per 10 ft for mains in steel-pipe systems.
12.1.5Deluge piping shall drain completely after every operation, because the open piping admits and retains test and discharge water at every low point.
12.2 Auxiliary Drains and Main Drain
12.2.1Drum drips and the main drain shall be drained as part of seasonal maintenance and after every release; missed drainage is a leading cause of corrosion and, in cold applications, of freeze damage.
○ Single drain valve at each trapped low point
○ Two-valve drum drip assembly (isolation and drain valves)
○ Per drawings — see pitch and drainage plan
Floor drain — interior heated valve room
Exterior discharge at grade
Discharge to storm system
12.2.3Auxiliary drains (drum drips) shall be provided at every trapped low point where water cannot drain back to the main drain by gravity, and shall be located so they can be reached for routine drainage.
12.2.4A main drain valve not smaller than 2 in. shall be provided at the valve assembly.
13 Water Supply and Fire Pump Interface
13.1Deluge systems impose a large simultaneous demand because every open device flows at once, and double-interlock pre-action systems must overcome the dry-pipe delivery delay; both frequently require a fire pump.
○ No — public supply adequate (see hydraulic calculations)
○ Yes — electric-driven fire pump per NFPA 20
○ Yes — diesel-driven fire pump per NFPA 20
○ Siamese (two 2-1/2 in. inlets)
○ Single 4 in. large-diameter-hose inlet
○ Siamese plus one 4 in. large-diameter-hose inlet
"AUTO SPKR — PREACTION" per NFPA 13
"AUTO SPKR — DELUGE" per NFPA 13
System-type sign plus zone identification
13.2The water supply shall meet the system demand plus the hose stream allowance with the NFPA 13 safety margin.
13.3Where a fire pump is provided, it shall be installed under Fire Pumps in accordance with NFPA 20, and the releasing matrix shall coordinate pump start with valve release so that pressure and flow are available when the valve trips. 13.4The fire department connection shall be provided per NFPA 13 and the IFC, with an automatic ball drip on the FDC supply piping and a sign identifying the system type.
14 Testing and Commissioning
14.1 Flushing and Hydrostatic Test
200400
200250300350400
Default: 200 psi
14.1.1The piping shall be flushed before sprinklers or open nozzles are installed, in accordance with NFPA 13 and NFPA 24, until the effluent runs clear.
14.1.2All piping shall be hydrostatically tested at 200 psi for 2 hours with no pressure loss and no visible leaks; where working pressure exceeds 150 psi the test pressure shall be working pressure plus 50 psi.
14.1.3After the witnessed hydrostatic test the system shall be thoroughly drained, including every auxiliary drain, before being placed in service.
14.2 Air Pressure Test (Pre-Action)
NOTE The air test detects joint leaks that sealed under water pressure but leak air. (14.2.1)
NOTE Deluge systems, being open to atmosphere, are not air-tested. (14.2.2)
○ 1.5 psi per 24 hours (NFPA 13)
○ Not applicable — deluge (open to atmosphere)
14.2.3Pre-action systems shall be air-tested at 40 psi for 24 hours with a pressure loss not exceeding 1.5 psi, in accordance with NFPA 13, after the system is drained from the hydrostatic test and before it is placed in service.
14.2.4Leaks shall be located by soap-bubble or ultrasonic testing and corrected before retest.
14.3 Valve Trip Test and Water Delivery Time
NOTE The trip test confirms the calculated trip-time and water-delivery values in practice. (14.3.1)
1560
152030405060
Default: 60 seconds
☐ Detection-initiated release (full sequence)
☐ Double-interlock: detection plus low-air, both required to release
☐ Manual release station operation
☐ Releasing matrix verified device-by-device
☐ Interlocks verified (HVAC, dampers, equipment shutdown)
☐ Water delivery time measured and recorded
14.3.2The pre-action or deluge valve shall be trip-tested by operating the detection system (and, for double-interlock systems, also venting the supervisory air) and confirming that the releasing control unit issues the release signal, the solenoid operates, the valve opens, and the alarm signals transmit.
14.3.3For pre-action systems the test shall confirm that water reaches the inspector's test connection at the most remote point.
14.3.4For double-interlock pre-action and deluge systems the measured water delivery time from operation to discharge shall not exceed 60 seconds, consistent with the dry-pipe water delivery rule.
14.3.5Where the field-measured time exceeds the calculated value the cause shall be investigated and corrected.
14.3.6The full releasing matrix shall be verified — each initiating device or zone, the cross-zoned logic, each releasing output, and each interlock (HVAC shutdown, damper, equipment power-down) — and the results recorded.
14.4 Partial-Flow and Solenoid Tests
14.4.1Where a full discharge test would damage the protected space — the usual case for deluge systems over transformers, electronics, or aircraft — the trip test may be performed as a partial-flow or no-flow test using the manufacturer's test arrangement.
○ Full-flow trip test (where discharge is acceptable)
○ Partial-flow test to test header
○ No-flow solenoid / logic test per manufacturer (sensitive areas)
14.4.2The acceptance test method shall be the one specified in the valve manufacturer's listing and instructions and accepted by the AHJ.
14.4.3At minimum, the releasing solenoid, the detection-to-release logic, and the alarm transmission shall be verified at acceptance.
14.5 Main Drain Test and Certificates
10180
20304050607080100120150
Default: 50 psi
14.5.1The main drain shall be fully opened with all supply valves open, and the static and residual flowing pressures recorded as the baseline for future NFPA 25 tests.
14.5.2The Contractor shall complete and sign the Contractor's Material and Test Certificate for Aboveground Piping (NFPA 13 Figure 29.1.1) and the NFPA 72 Record of Completion for the detection and releasing system, and shall schedule an acceptance inspection with the AHJ.
14.5.3The system shall not be placed in service until the AHJ has witnessed the required tests and issued approval.
15 Installation
15.1 Pipe Routing and Coordination
NOTE Working drawings approved by the AHJ govern the routing, sizing, and arrangement of all piping. (15.1.1)
NOTE Routing changes are particularly consequential because they affect system volume, water delivery time, drainage, and the open-nozzle hydraulic balance on deluge systems. (15.1.2)
15.1.3Deviations from the approved working drawings require a revised submittal or written approval from the Engineer of Record and the AHJ.
15.1.4Piping shall be routed to maintain the required pitch; where obstructions force a deviation, an auxiliary drain shall be provided at the resulting low point.
15.1.5The detection layout, releasing control unit location, and conduit routing shall be coordinated with the sprinkler piping so that detector spacing and releasing circuit survivability are not compromised by field changes.
15.2 Cutting, Fabrication, and Protection
15.2.1Pipe shall be cut square, reamed to remove burrs, and grooved to the coupling manufacturer's dimensions.
15.2.2All open pipe ends shall be capped when work is not in progress to keep out debris, which is especially damaging to the small orifices in the valve trim, the releasing solenoid, and open deluge nozzles.
15.2.3Galvanized pipe field-cut, threaded, or welded shall be touched up with cold-galvanizing compound.
15.2.4Detection devices shall be protected from construction dust and shall not be placed in service until the space is clean enough that nuisance operation will not occur.
16 Hangers and Seismic Bracing
NOTE Seismic joint failure is especially consequential on these systems because loss of supervisory air or damage to the releasing/pilot lines can produce a trouble condition or, on a single-interlock system already in the released state, an unintended discharge. (16.1)
○ No — SDC A or B
○ Yes — SDC C
○ Yes — SDC D, E, or F (full bracing per NFPA 13 Chapter 18)
16.2Hangers shall be listed for fire protection use and installed per NFPA 13 Chapter 17, sized for the water-filled pipe weight because the pipe fills with water during hydrostatic testing and after every release.
16.3Where the building is in Seismic Design Category C, D, E, or F per ASCE 7 and the IBC, lateral and longitudinal seismic bracing shall be provided per NFPA 13 Chapter 18, with flexible couplings at the prescribed locations.
17 Delivery, Storage, and Handling
17.1Detectors and the releasing control unit are electronic devices and shall be protected from construction dust and humidity until the space is ready.
Indoor conditioned storage, original packaging
Indoor unconditioned storage, protected from moisture
Per manufacturer requirements
17.2Sprinklers, open nozzles, valves, detectors, and the releasing control unit shall be delivered in the manufacturer's original packaging and stored indoors in a clean, dry, conditioned space protected from impact, moisture, dust, and temperature extremes.
17.3Sprinklers and open nozzles shall not be dropped or otherwise subjected to impact, and any device that has been dropped or shows physical damage shall be discarded, not installed.
17.4Pipe shall be stored off the ground with end caps in place to keep the interior clean.
18 Warranty
18.1The warranty shall run from the date of substantial completion and shall cover the complete installed system including pipe, fittings, hangers, seismic bracing, the pre-action or deluge valve, the releasing control unit, detectors, the release solenoid, the air or nitrogen supply (pre-action), alarm and supervisory devices, the fire department connection, and all specialties.
1 year from substantial completion
2 years from substantial completion
○ 4 hours maximum for restoration or alternative protection
○ As required by AHJ impairment plan
18.2The Contractor shall warrant all materials and workmanship against defects for the project warranty period, running from the date of substantial completion.
18.3Sprinklers and open nozzles carry individual manufacturer's limited warranties that the Contractor shall pass through to the Owner.
18.4Warranty service shall include investigation of any persistent supervisory-trouble or low-air conditions, which on these systems can indicate a developing joint leak, a detector fault, or a releasing-circuit problem that was not present at acceptance but emerges as the installation ages.
18.5Any impairment shall be handled per NFPA 25 impairment procedures with prompt notification to the Owner, the monitoring station, the fire department, and the insurer.
19 Spare Parts
19.1The Contractor shall turn over the spare releasing components recommended by the valve and panel manufacturers, because a failed solenoid or detector impairs the entire system and these items are not always locally stocked.
6 devices (≤300 installed)
12 devices (301–1,000 installed)
24 devices (>1,000 installed)
☐ Spare release solenoid
☐ Spare detectors (each type installed)
☐ Spare valve trim gaskets / diaphragm
☐ Sprinkler wrench for each sprinkler type
19.2The Contractor shall provide a cabinet of spare sprinklers (or spare open nozzles, for deluge systems) and one sprinkler wrench of each type, mounted in the valve room or adjacent mechanical room, in accordance with NFPA 13.
19.3The cabinet shall contain at minimum six devices for systems with up to 300 installed, 12 for 300 to 1,000, or 24 for systems over 1,000, and shall represent each type, orifice/K-factor, temperature rating (closed heads), and finish installed.
19.4The Contractor shall turn over at minimum a spare release solenoid and the recommended spare detectors recommended by the valve and panel manufacturers.
20 Ongoing Inspection, Testing, and Maintenance
20.1The system shall be inspected, tested, and maintained throughout the life of the building in accordance with NFPA 25 for the water-based portion and NFPA 72 for the detection and releasing portion, current adopted editions.
○ Combined service agreement (sprinkler and fire alarm contractors)
○ Separate agreements for NFPA 25 and NFPA 72 work
○ Owner-performed where qualified per NFPA 25 / NFPA 72
20.2NFPA 25 establishes intervals for inspecting components, testing alarm and supervisory devices, conducting main drain tests, performing the valve trip test, and servicing the air or nitrogen supply.
20.3NFPA 72 establishes intervals for testing detectors, the releasing control unit, batteries, and the releasing circuits.
20.4Supervisory air/nitrogen pressure and valve-room heating shall be inspected weekly or monthly on pre-action systems; waterflow and supervisory alarms shall be tested quarterly; the valve shall receive an annual full trip test including the complete releasing sequence; detector sensitivity shall be tested periodically per NFPA 72; and every auxiliary drain shall be drained seasonally and after every release.
20.5The Owner shall maintain a service agreement with qualified fire protection and fire alarm service contractors, and records of all inspections and tests shall be retained on-site and available to the AHJ.